Christchurch Central MP Nicky Wagner will announce her political future next week.

Wagner was seen engrossed in what appeared to be a serious conversation with Prime Minister John Key at the Ballantynes cafe on Wednesday afternoon but refused to reveal what they talked about.

"It was actually a private conversation . . . we talked about all kinds of interesting things," she said yesterday.

Speculation has been rife for weeks she may stand down at this year's election after proposed electorate boundary changes to her seat prompted her to describe it as "unwinnable".

She will reveal her decision to National MPs at an all-day caucus next Friday before confirming it publicly.

"Everybody will be there. I'll just finalise what I'm going to do and do it properly."

Those and other comments suggest she could be calling time on her nine-year stint as an MP in the city.

Her potential retirement would make her the 11th National MP to quit ahead of the election.

Wagner unsuccessfully stood for National in the Christchurch Central seat at the elections in 2002, 2005 and 2008. She was elected into Parliament as a list MP in 2005 but outright won the traditional Labour seat by 47 votes in 2011.

The result on election night was a dead heat between her and Labour's Brendon Burns but she won after a recount and special votes were counted.

But Wagner has been openly frustrated with possible new electorate boundaries that could see Government-friendly areas shifted to other seats. Those proposed changes made Christchurch Central "almost unwinnable" for National.

Earlier this year, she told The Press it would be "really disappointing to lose" after wresting the seat from Labour in 2011.

Wagner doubted she would be high enough on the party list to be returned to Parliament that way and questioned how she could "fight an election I could lose".

The man tipped to be Labour's candidate in the seat declined to comment on Wagner's impending announcement.

Tony Milne, who is the party's Christchurch Central spokesman, said its campaign would be "focused on the issues that matter and not on our opponents".

National officials have said its candidate would be picked after boundary changes were finalised in April.